New blood test accurately predicts Alzheimer’s years before first symptoms: ScienceAlert

A new type of blood test can detect a hidden toxin behind Alzheimer’s disease years before a patient shows symptoms of memory loss or confusion.

If the proof-of-concept can be further tested and scaled up, the test could significantly speed up diagnosis, giving millions of patients answers and access to appropriate care long before their disease progresses.

Researchers at the University of Washington (UW) have created the new blood test. It is designed to capture a molecular precursor in the blood that can cause proteins to misfold and accumulate in the brain, eventually forming amyloid beta (Aβ) plaques.

Aβ plaques are a well-known feature of Alzheimer’s disease, but their role in cognitive decline is uncertain. Historically, these extracellular plaques have been considered an early trigger of neuronal dysfunction and loss, ultimately leading to cognitive decline.

However, recent studies have shown that Aβ plaques are only present in a third of Alzheimer’s patients and are sometimes present in the brains of people who do not show cognitive deficits.

In other words, extracellular Aβ plaques in the brain are not necessarily toxic per se, but may arise from notoriously difficult-to-detect molecular toxins.

These toxins are essentially the functional versions of Aβ found inside cells. They’re known as “toxic Aβ oligomers,” and some scientists believe they could subtly damage neurons from afar, somehow predisposing cells to extracellular plaques and clumps.

Scientists are still figuring out the details, but the hypothesis led the UW researchers to do an impressively accurate soluble oligomer binding assay, nicknamed SOBA.

The researchers first examined SOBA in the blood plasma of 310 participants. Some participants had mild cognitive impairment or Alzheimer’s disease, while others had good cognitive health.

By measuring toxic Aβ oligomers in blood plasma, SOBA selected all 53 participants with Alzheimer’s who were later confirmed to have the disease after death.

Meanwhile, in the control group, SOBA detected oligomers in blood plasma samples of 11 subjects. Ten of these participants were later diagnosed with mild cognitive impairment or Alzheimer’s.

“What clinicians and researchers have wanted is a reliable diagnostic test for Alzheimer’s disease – not just an assay that confirms a diagnosis of Alzheimer’s, but one that can also detect signs of the disease before cognitive decline occurs,” says industrialist Valerie Daggett from the UW. .

“This is important for human health and for all research into how toxic amyloid beta oligomers persist and cause the damage they do. What we show here is that SOBA can be the basis of such a test.”

And that’s not all SOBA can do. After all, Alzheimer’s is not the only disease characterized by toxic oligomers.

The misfolded proteins also appear to be associated with Parkinson’s disease, type II diabetes and Lewy body dementia, meaning that SOBA could one day be modified to pick up early markers of these other diseases.

Other tests have also attempted to measure markers of Alzheimer’s disease, but with varying levels of success.

In 2018, for example, a blood test that also detects Aβ precursors predicted the onset of Alzheimer’s up to 30 years before cognitive deficits even began to appear.

SOBA, the researchers say, can make similar predictions.

In current clinical practice, only blood tests that measure the genes associated with Alzheimer’s disease are used, but these tests are not as good at predicting who will actually go on to develop the disease.

With tests like SOBA performing so well, this could be on the verge of changing.

The study was published in PNAS.

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